During the continuous evolution of the Code Division Multiple Access (CDMA) networks, interoperability with the Long Term Evolution (LTE) network is a development trend of the networks. A commercial CDMA network is evolved to the LTE network, which is not a simple substitution process, and instead, there will be a long coexistence period therebetween, during which interconnection and interworking between the two wireless networks are indispensable.
One of the evolved High Rate Packet Data (HRPD)-LTE interoperability functions is to support an idle switch of an access terminal from the HRPD to the LTE. In order to support that function, a series of protocol processes are defined in the HRPD system. However, there are still two problems needed to be considered:
Firstly, after the terminal is switched to the LTE network in an idle state, the HRPD access network and the terminal will continue to maintain air interface session information of the terminal in the HRPD network through a session maintenance timer, since the HRPD air interface session negotiation is time-consuming, and continuously maintaining the air interface session information for a period of time can avoid influencing the switch performance and the user experience due to the air interface session negotiation after the terminal switches back to the HRPD quickly. In the process of maintenance of the HRPD air interface session, the terminal and the HRPD access network can transmit a session keep-alive message to the counterpart respectively and wait for a response message from the counterpart. However, in the case that the terminal has been attached to the LTE network and there is no tunnel interface between the HRPD access network and a Mobility Management Entity (MME) of the LTE, the HRPD access network will still transmit the air interface session maintenance message to the terminal due to failing to know that it has been switched to the LTE network in an idle state, which will result in a waste of a paging channel capacity of the HRPD network, thereby influencing the HRPD network performance.
Secondly, the priority based idle reselection method makes the terminal always tend to a network with a high priority. According to the current idle reselection method, if a common priority is broadcast in an HRPD overhead message, the terminal will always perform reselection according to the common priority, which is commonly used by the terminal. While in general, the operator will set the priority of the LTE network to be higher than that of the HRPD network, and thus all terminals in an idle sate will always tend to the LTE network. Due to a long-term coexistence between the LTE network and the HRPD network, the operators desire to control the selection of a network to which the terminal in an idle state is attached according to a certain strategy, thereby implementing an equilibrium distribution of users and effective operation of networks, thus a condition that one network has a heavy network load and the other network is vacant is avoided.